2,751,086. June 9, 1956 APPARATUS FOR THE SEPARATION OF FARTICLES, PARTICULARLY FIBRES, THAT ARE SUSPENDED IN A LIQUID. Filed July 6, 1952

Transcription

1 June 9, 1956 O. B. RdSRJESON APPARATUS FOR THE SEPARATION OF FARTICLES, PARTICULARLY FIBRES, THAT ARE SUSPENDED IN A LIQUID Filed July 6, Sheets-Sheet l 2y

2 June 19, 1956 Filed July 16, 1952 APPARATUS FOR THE FIBRES O. B. BÖRJESON SEPARATION OF PARTICLES,, THAT ARE SUSPENDED IN A LIQUID PARTICULARLY 4. Sheets-Sheet 2 ZWVAW7OA Ozov 366AA a3.jesow A77 AWay

3 June 19, 1956 O. B. BÖRJESON APPARATUS FOR THE SEPARATION OF PARTICLES, PARTICULARLY FIBRES, THAT ARE SUSPENDED IN A LIQUID Filed July l6, l Sheets-Sheet 3 ZA/VA/w72a O&OV BaGeR Aée.Jesow 8 22 A77 Oa/VAY

4 June 19, 1956 O. B. BÖRJESON APPARATUS FOR THE SEPARATION OF PARTICLES, PARTICULARLY FIBRES, THAT ARE SUSPENDED IN A LIQUID Filed July 16, l Sheets-Sheet 4 a 7. ZZ Z2 A/YVAA/7 oa Olov A/A6AA A3eJasow ada/vay

5 United States Patent Office Patented June 19, 1956 APPARATUS FOR THE SEPARATION OF PARTI CLES, PARTICULARLY FIBRES, THAT ARE SUS PENDED IN A LIQUID Olov Birger Börjeson, Bromma, Sweden, assignor to Seje & Thurne Aktiebolag, Stockholm, Sweden, a corpora ion of Sweden Application July 16, 1952, Serial No. 299,199 Claims priority, application Sweden April 3, Claims. (C ) The present invention refers to such apparatus for the separation of particles suspended in a liquid that are of the type particularly made use of in cellulose factories for the purification of the so-called back water and for the recovery of fibres suspended therein. The invention relates especially to apparatus of the kind consisting of a liquid container and a strainer drum arranged therein and partly submerged in the liquid, said drum being adapted to rotate, while the liquid flows through the cylindrical shell of the drum, which is perforated or consists of wire gauze, the fibres being thus caused to deposit on the out side of the drum and to be separated from the drum at a point located above the surface of the liquid. The liquid which is to be purified in this manner generally contains both long and short fibres in varying proportions. In con sideration of this fact it was hitherto necessary to select the width of the meshes of the shell of the strainer drum comparatively small, or to resort to relatively complicated means for repeated straining of the liquid for the purpose of achieving an effective separation of the short-fibred material as well. The employment of a strainer gauze with too fine meshes involves the drawback that the work ing capacity of the apparatus, that is to say the quantity of liquid flowing through the strainer per unit of time and unit of surface is reduced. The object of the present invention is to increase the fibre-separating capacity of the strainer drum without appreciably reducing its capac ity to let the purified liquid therethrough. To this end the apparatus according to the invention is provided with a means for applying an auxiliary suspension onto the portion of the shell of the strainer drum located above the Surface of the liquid in the container, in a manner Such that the particles separated from this suspension form a filter-like layer on the outer surface of the strainer drum. By the fact that this fibre layer is applied to the portion of the drum situated above the liquid surface, While the drum performs its rotating movement, the fibre layer will remain on the drum also during the passage through the liquid in the container, so that the whole of the portion located underneath the liquid surface will be covered by said fibre layer, which will thus act as a filter which absorbs and separates the short fibres as well as the long ones. Hereby the straining capacity of the drum is increased, without the capacity of the drum to per mit the passage of water therethrough being reduced in any appreciable degree. As an auxiliary suspension a fibre Suspension is preferably made use of, which is more concentrated than the Suspension flowing through the liquid container. The means by which said auxiliary Suspension is applied is preferably made controllable, so that the degree of concentration of the auxiliary Suspen sion may be varied with respect to the nature or composi tion of the fibrous material in the liquid to be purified. The invention will be described more closely with refer ence to the accompanying drawings, which illustrate a form of embodiment of an apparatus constructed in ac cordance with the invention for the separation of fibres from the back water in cellulose factories. Fig. 1 shows a cross section through the apparatus and the strainer drum. Fig. 2 shows details to a larger scale. Fig. 3 shows a partly sectioned elevation of the apparatus, the strainer being conceived of as being removed from the upper half of the strainer drum. Fig. 4 is a plan view of the apparatus. Fig. 5 is a view to a larger Scale of the means for applying the auxiliary suspension onto the strainer drum and for the separation of the layer of fibres from the drum. The strainer drum comprises a cylindrical shell 1, which in the example shown is taken to be perforated but which may consist of one or more layers of wire gauze, an end wall 2, which at the right-hand end in Fig. 3 closes the space enclosed by the shell of the drum, and an end wall 3 provided with a number of circular aper tures, which in Fig. 1 are indicated by chain-dotted cir cles 4 and through which the interior of the drum com municates with a cylindrical space 5 located outside said end wall 3. The strainer drum is rotatably mounted in the end walls 6, 7 of a liquid container 8 enclosing the strainer drum, the jacket wall 9 of the container having the cross sectional shape shown in Fig. 1 and fitting to the drum. The end wall 2 of the drum is mounted by means of a bearing sleeve 10 on a hollow bearing pin 1 secured in the wall 7, and the end wall 3 is mounted in a similar manner by means of a bearing sleeve 2 on a hollow bearing pin 13 secured in the wall 6, this bear ing pin 13 being closed at the outer end thereof by means of a removable cover 14. The end walls 2, 3 are rein forced by means of radial ribs or spokes 15, 16, 17 and are internally braced relatively to each other by means of longitudinally extending rods 18 arranged inside the shell of the drum and by tubular pieces 19 thrust onto said rods, these tubular pieces forming distance members between a number of sheet-metal rings 20 forming a sub structure and support for the shell of the drum. The strainer drum is adapted to be operated by an electric motor 21, Fig. 4, said motor driving a shaft 23 through the intermediary of a worm gearing 22 and said shaft 23 being mounted in the wall 6 and adapted in turn to drive the drum by means of a pinion 24 and a gear wheel 25 secured to the end wall 3 of the drum by means of bolts 26. The gearing 24, 25 is arranged with in the abovementioned cylindrical space5, the cylindrical jacket Wall of which is constituted in part by cylindrical flange 27 secured to the wall 6 and in part by a cylindrical flange 28 secured to the end wall 3. The intermediate Space between these flanges is sealed outwardly by means of a rubber ring 29 which is secured to the flange 27 by means of a metal ring 30. Connected to the wall 6 is an outlet pipe 31 communicating with the space 5, said out let pipe having a valve 32 inserted therein. The liquid container 8 is mounted on a number of posts 33, Fig. 1, which are connected to the end walls 6, 7 of the container by means of horizontal girders 34 secured to these end walls. The lower portion of the shell 9 of the liquid container is formed into a channel 35 to col lect sludge and non-separated fibres, which may be emp tied through doors 36 into a drain channel 37 in the floor 38. The means for applying the auxiliary Suspension is shown most clearly in Fig. 5. It consists of a filling receptacle 39 in the form of a chute, which preferably extends all over the length of the strainer drum and which is provided with an overflow 40, over which the Suspension flows to an equalizing chute 41, which like wise extends all over the length of the strainer drum, and which is in turn provided with an overflow 42 con tinuing in a sloping wall 43, along which the Suspension flows down onto the shell 1 of the drum. The auxiliary Suspension is Supplied through a pipe 44 and a horizontal

6 3 distributing pipe 45 connected thereto, from which the suspension flows directly down into the receptacle 39. To prevent movements in the liquid beside the over flow 40, a vertical baffle plate 46 is fitted between the overflow and the point of inflow of the suspension, which latter must then pass underneath the lower edge of the baffle plate 46 to reach the overflow 40. When re quired, the suspension may be diluted with water through a pipe 47 to control the degree of concentration. The receptable 39 is arranged on a horizontal shelf 48, which is secured to a longitudinally extending girder 49 mounted so as to permit of being raised and lowered in the frame of the apparatus. The shelf also carries the suction box 50 connected to an evacuating pump 51, Fig. 4, said box communicating through a hole in the shelf with a space 52 having the means for the separation of the fibre layer from the drum arranged therein. The latter means consists of a hollow roller 53 extending in the longitudinal direction all over the length of the strainer drum and adapted to rotate in contact with the shell of the drum, the fibre layer being thus compressed and trans ferred onto the roller by adhesion and entrained by the roller, tintil it reaches the edge of a scraper 54 bear ing on the surface of the roller. The fibrous pulp separ rated from the roller passes in the transverse direction over the scraper and over an inclined plate 55, which is secured to a bar 56 carrying the scraper. Then the pulp passes over the scraper, water is being Supplied from a pipe 57 to facilitate the downward movement of the fibrous pulp. The fibrous pulp falls from the lower edge of the plate 55 down onto the outside of a sloping plate 58, along which the pulp is moved further to a collecting pocket 59, from which the pulp escapes through an outlet. On one side of the roller 53, the space 52 is closed by a curved wall 60, which is sealed by means of a rubber lip 61 against the surface of the strainer drum shell. On the other side, the space 52 is limited by the scraper 54 and the plate 55 as well as by a vertical wall 62 extending from the shelf 48 and by an elastic flange 63 connected to said wall and bear ing loosely with the outer edge thereof on the plate 55 or terminating at some distance from the latter. Through this limitation of the space about the roller 53 a powerful suction of air through the space 52 is created, which is particularly the case in the restricted portion 64 of said space located adjacent to the shell of the strainer drum, whereby the separation of the fibre layer from the 5 O mounted at the ends thereof in arms 74, which are Swingable about the axis 68 and connected through an arm 75 and a pivot 76 to a lever 77, on which a weight 78 is adjustably arranged for the purpose of controlling the turning moment transferred to the arms 74. The shaft 76 is mounted in a member 79 of the frame, said member being rigidly connected with the girder 49. When the strainer drum rotates in the direction indi cated by the arrow in Fig. 1 and the auxiliary suspension is applied in an adapted quantity and in a suitable con centration a filter-like layer of fibres is formed on the portion of the drum shell located above the water surface 80 in the liquid container. The fibre layer is retained in part by the adhesion against the shell and in part through the external pressure created by the vacuum within the drum. The fibre layer will thus remain on the shell during its passage through the liquid in the container and then serves as a filter for the liquid flowing through the shell of the drum, the fibres suspended in the liquid being thus separated and caused to deposit on said filter layer, which thus increases successively in thickness. When the fibre layer reaches the takeoff roller 53, the same will be separated from the drum in the manner previously described. The liquid in the auxiliary suspension flows off through the shell of the strainer drum at the portion of the shell located above the surface of the liquid, a portion of the fibres being then caused to follow the water escaping adjacent to the point of application. The water escaping in this manner and the fibres entrained therewith are collected in an elongated collecting receptable 81 arranged within the strainer drum underneath the point of application, said collecting receptacle being carried by the fixed journals of the drum at one end of a rod 82 and at the other end by a pipe 83 opening into the central bore of the journal 11 and serving as an outlet for water and fibres collected in the receptacle 8. Connected to the outer end of the bore of the journal 11 is a pipe 84, which opens into an aperture 85 in the end wall 7 of the liquid container. The mixture of water and fibres escaping from the receptacle 81 is thus transferred to the liquid space in the liquid container to mix with the fibrous suspension therein. The fibrous suspension to be subjected to straining is supplied to the liquid container through a pipe 86, Fig. 1, the Suspension then flowing into a space 87, which is screened off by a baffle plate 88 from the remaining liquid Space in the container, into which space the suspension flows through a narrow passage 89 between the shell drum is facilitated. Fibres that might be entrained with the drum are scraped off the latter at the rubber lip 61 to follow the air round the roller 53 to the upper portion 50 wall 9 and the lower edge of the baffle plate. This pre of the space 52. By reason of the vacuum created by vents motions in the liquid caused by the inflowing sus the suction box air may also be sucked off the space pension from being transferred to the portion of the 65, which is limited by the container 39, the chute 41, liquid space surrounding the strainer drum. the wall 43, the strainer drum shell and the Wall 60. On account of the resistance to flow of the filter layer The fibres that might be entrained with the drum past the there is a head between the liquid level 89 outside the lip 61 are washed off the surface of the drum by means drum and the liquid level 90 inside the drum, which of water jets from a pipe 66. To provide for a good latter corresponds to the level of the discharge pipe 31. tightening effect between the sloping wall 43 and the The vacuum may be controlled to a certain extent by shell of the drum said wall is provided at the lower edge choking the valve 32. However, a special valve 91, Fig. thereof with a rubber lip 67 bearing with the outer 60 1, is preferably used for this purpose, said valve being edge thereof on the drum. arranged in the outer wall 6 of the space 5, Fig. 3. In The angle bar 56 carrying the scraper 54 is Swing the example shown, this valve is arranged to be auto able about an axis 68 in order to facilitate a Swinging matically opened and closed in dependence on the liquid movement of the scraper into and out of its workingpo level 80. The control is effected by means of a float 92 sition and to facilitate setting of the scraper at a suitable 35 arranged in the space 87, said float being connected to pressure agains the surface of the roller 53. For this the valve 9 by means of a lever 94 pivotally mounted purpose the angle bar 56 is connected through links 69, at 93 and a link connection 95, 96, indicated in part 70 to a lever 71, as will appear from Fig. 2, said lever only, said valve taking the form of a throttle valve. The being swingable about an axis 72 and provided with a supply of suspension through the pipe 86 is so adapted weight 73 which is adjustable along the arm, by means 70 that the liquid will normally keep at the level shown of which weight a turning moment may be transferred in Fig. 1. However, since the liquid level 80 is also to the angle bar 56 to achieve a suitable bearing pressure dependent on the vacuum within the strainer drum, between the scraper 54 and the roller 53. certain control of the liquid level may be achieved by a To provide for a suitable bearing pressure between float control of the valve 91 in the manner set forth. the roller 53 and the shell of the drum, the roller is is When the liquid level falls, the valve opening is increased

7 5 while the resistance to flow of the valve 91 is reduced, the vacuum being thus reduced, which is also the case with the rate of flow of the liquid through the shell of the drum, so that the liquid level is again caused to rise. When the liquid level rises, a control will be effected in an analogous manner in the opposite direction. The discharge valve 32, Fig. 3, may be arranged to be con trolled in a corresponding manner. In this way the con trol may proceed automatically at the maintenance of a suitable, relatively low vacuum, such as 150 mm., within the strainer drum, the liquid surface 90 being thus caused to keep at a corresponding level above the discharge valve 32. Through the rotation of the strainer drum, the liquid layer adjacent to the shell of the drum is brought into movement round the circumference of the drum from the front portion of the liquid space to the remote por tion thereof. Consequently, there will be an accumula tion of fibres in the remote portion 97 of the liquid space, which may under unfavourable circumstances in fluence the filter layer 98 on the drum, so that said layer will be injured and is caused to work loose in part. What I claim is: 1. An apparatus for separating fibers from a liquid fiber suspension, comprising a walled container for the liquid suspension, a rotary strainer drum comprising a cylindrical shell mounted for rotation in a predetermined direction in the container and dimensioned to provide a free liquid space between the cylindrical shell of the drum and the surrounding wall of the container, means for depositing an auxiliary fiber suspension on the upper, descending surface of said drum, whereby to form a continuous fibrous filter layer on the drum, said means comprising a supply receptacle for the auxiliary fiber suspension, an overflow chute receiving auxiliary sus pension from said receptacle extending transversely over the entire length of the top portion of the strainer drum and having a sloping bottom tightly adjoining the shell of the drum, a take-up roller at the rising side of the strainer drum near said chute for discharging from the strainer drum the fibers deposited thereon, said roller positioned to adjoin tightly the fiber-covered drum, means defining an air passage between said chute and said take up roller, and a suction box communicating with the interior of the strainer drum through said air passage. 2. An apparatus for separating fibers from a liquid fiber suspension, comprising a walled container for the liquid suspension, a rotary strainer drum comprising a cylindrical shell mounted for rotation in a predetermined direction in the container and dimensioned to provide a free liquid space between the cylindrical shell of the drum and the surrounding wall of the container, means for depositing an auxiliary fiber Suspension on the upper, descending surface of said drum, whereby to form a con tinuous fibrous filter layer on the drum, said means com prising a supply receptacle for the auxiliary fiber sus pension, a distributing chute for the auxiliary suspension discharged from said rceptacle extending transversely over the entire length of the top portion of the strainer drum and adjoining the shell of the drum, a take-up roller at the rising side of the strainer drum near said chute for discharging from the strainer drum the fibers deposited thereon, said roller positioned to adjoin tightly the fiber-covered drum, and means defining an air pas sage between said chute and said take-up roller. References Cited in the file of this patent UNITED STATES PATENTS Re. 21,201 Qviller Sept. 5, ,212 Gaara et al Sept. 8, , 183 Gaara Mar. 8, ,360,684 Roberts Nov.30, ,867,930 Traquair July 19, ,742 Hillier June 20, ,092, 111 Dons et al Sept. 7, ,100,149 Qviller Nov. 23, ,108,231 Nash Feb. 15, ,154,719 Berry Apr. 18, ,327,543 Moor Aug. 24, ,352,304 Young June 27, ,449,902 Kiersted Sept. 21, ,598,606 Robison May 27, ,609,732 Breyfogle Sept. 9, 1952 FOREIGN PATENTS 311,934 Germany Nov. 11, ,646 Norway Mar. 10, ,779 Sweden Jan. 18, ,153 Norway Oct. 12, ,534 Sweden Dec. 7, ,622 Canada Mar. 14, 1950